JP2019164994A - Mechanically sealed tube for laser sustained plasma lamp and production method for the same - Google Patents

Abstract

To mitigate life degradation caused by sealing of components in a laser sustained plasma lamp.SOLUTION: A chamber assembly 330 configured to contain an ionizable material comprises a sapphire tube, an ingress sapphire window 340, a first metal seal ring 310 configured to seal against the chamber tube ingress end and the ingress sapphire window 340, an egress sapphire window 342, and a second metal seal ring 322 configured to seal against the chamber tube egress end and the egress sapphire window 342. A mechanical clamping structure 350, 355 external to the chamber assembly 330 is configured to clamp across at least a portion of the ingress sapphire window 340 and the egress sapphire window 342.SELECTED DRAWING: Figure 3A

Description

  The present invention relates to a lighting device, and more particularly to a high-intensity arc lamp.

  A high-intensity arc lamp is a device that emits high-intensity light. The lamp typically includes an anode and a cathode used to excite the gas (ionizable medium) in the chamber, along with a gas containment chamber, such as a glass bulb. A discharge occurs between the anode and the cathode, and power is supplied to the excitation (eg, ionized) gas to maintain the light emitted by the ionized gas during operation of the light source.

  FIG. 1 shows a three-dimensional view and a cross-sectional view of a prior art low watt parabolic xenon lamp 100. The lamp is generally composed of metal and ceramic. The filling gas xenon (Xe) is inert and nontoxic. The lamp subassembly can be constructed by high temperature brazing in a fixture that constrains the assembly to tight dimensional tolerances. FIG. 2 shows some of these lamp subassemblies and fixtures after brazing.

  In the prior art lamp 100, there are three main subassemblies: cathode, anode, and reflector. The cathode assembly 3a includes a lamp cathode 3b, a plurality of columns 3c that hold the cathode 3b on the window flange, a window 3d, and a getter 3e. The lamp cathode 3b is a small pen-sealed part made of, for example, triated tungsten. In operation, the cathode 3b moves across the lamp arc gap and emits electrons that impinge on the anode 3g. As electrons are emitted from the cathode 3b, the cathode tip must maintain high temperature and low electron emission in order to function.

  The cathode support 3c securely holds the cathode 3b in place and conducts current to the cathode 3b. The lamp window 3d may be ground and polished single crystal sapphire (AlO2). Sapphire allows the thermal expansion of the window 3d to match the flange thermal expansion of the flange 3c, thereby maintaining a hermetic seal over a wide operating temperature range. Heat is transported to the flange 3c of the lamp by the thermal conductivity of sapphire and the heat is evenly distributed, so that the window 3d is prevented from cracking. The getter 3e surrounds the cathode 3b and is placed on a support column. The getter 3e absorbs pollutant gases generated in the lamp during operation and extends lamp life by preventing contaminants from contaminating the cathode 3b and carrying unwanted material to the reflector 3k and window 3d. The anode assembly 3f includes an anode 3g, a base 3h, and a tube 3i. The anode 3g is generally made of pure tungsten and has a shape that is significantly duller than the cathode 3b. This shape is mainly the result of discharge physics that the arc spreads at the electrical connection point of its anode. The arc is typically somewhat conical, with the apex of the cone touching the cathode 3b and the base of the cone touching the anode 3g. The anode 3g is larger than the cathode 3b and conducts more heat. About 80% of the conducted exhaust heat in the lamp is conducted out through the anode 3g and 20% is conducted through the cathode 3b. Since the anode is generally configured to have a low thermal resistance path to the lamp heat sink, the lamp base 3h is relatively large. The base 3h is made of iron or other thermally conductive material to conduct a heat load from the lamp anode 3g. The tube making 3i is a port for emptying the lamp 100 and filling it with xenon gas. After filling, the tube 3i is sealed and clamped or cold welded using, for example, a hydraulic tool, so that the lamp 100 is disconnected and simultaneously disconnected from the filling and processing station. The reflector assembly 3j includes a reflector 3k and two sleeves 3l. The reflector 3k may be a substantially pure polycrystalline alumina body that is overcoated with a high temperature material to provide a reflective surface for the reflector. The reflector 3k is then sealed to the sleeve 31 and the reflective coating is applied to the overcoated inner surface.

  In operation, the anode and cathode become very hot due to the discharge caused to the ionized gas between the anode and cathode. For example, an ignition xenon plasma may burn at 15,000 C or higher, and a tungsten anode / cathode may melt at about 3600 C degrees or higher. The anode and / or cathode can wear and release particles. Such particles can impair lamp operation and lead to anode and / or cathode degradation.

  For existing laser-sustained plasma lamps constructed by conventional brazing methods, these brazing interfaces must be cooled to around 300 degrees Celsius for envelope and sealing consistency over the life of the product. . Due to the cooling, the operating temperature of the lamp is not ideal to minimize gas turbulence in the envelope of such lamp. Operation at higher lamp envelope temperatures has been shown to significantly reduce gas turbulence, resulting in higher plasma stability and, as a direct consequence, higher brightness across the aperture. Similarly, some existing laser-sustained plasma lamps are formed of a material that cannot accommodate mercury-enhanced fill gas to obtain high internal operating pressure. It is therefore necessary to address one or more of the above-mentioned drawbacks.

  Embodiments of the present invention provide a mechanically sealed tube for a laser-sustained plasma lamp and a method for manufacturing the same. Briefly stated, the present invention relates to a laser sustained plasma lamp having a sealed mechanical pressurized sealed chamber assembly configured to contain an ionizable material. The chamber assembly includes a chamber tube, an inlet sapphire window, a chamber tube inlet end, a first metal sealing ring configured to seal against the inlet sapphire window, an outlet sapphire window, a chamber tube outlet end and an outlet. Surrounded by a second metal sealing ring configured to seal against the sapphire window. A mechanical fastening structure external to the chamber assembly is configured to span and fasten at least a portion of the entrance sapphire window and the exit sapphire window. The entrance sapphire window and the exit sapphire window are not connected to the chamber tube by welding and / or brazing.

  Other systems, methods, and features of the present invention will become apparent to those skilled in the art upon review of the following drawings and detailed description. Such additional systems, methods, and features are included in this description, are within the scope of the invention, and are protected by the following claims.

  The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The components in the drawings are not necessarily to scale, emphasis is placed upon clearly illustrating the principles of the present invention. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

It is an exploded view of the schematic diagram of the high-intensity lamp of the prior art. It is sectional drawing of the schematic diagram of the high-intensity lamp of the prior art of FIG. It is a typical partial side view of 1st Embodiment of a sealed high-intensity lamp. It is a typical perspective view of the lamp | ramp of FIG. 3A. 3B is a schematic local view detailing the chamber of the lamp of FIG. 3A. FIG. 4B is a schematic partial exploded view of the chamber of FIG. 4A. FIG. FIG. 4B is a schematic exploded perspective view of the chamber of FIG. 4A. 3B is a schematic partial side view of a sealed portion of the lamp of FIG. 3A. FIG. 3B is a schematic diagram of a pressurized tooling chamber used to manufacture the sealable pressurized laser-maintained plasma lamp of FIG. 3A. FIG. 2 is a flowchart of an exemplary embodiment of a method for forming a sealable pressurized laser sustained plasma lamp.

  The following definitions serve to interpret terms that apply to the features of the embodiments disclosed herein and are intended only to define elements in the present disclosure.

  In this disclosure, a lens refers to an optical element that changes the direction / shape of light passing through the optical element. In contrast, the mirror or reflector changes the direction / shape of the light reflected from the mirror or reflector.

  In this disclosure, a direct path refers to a path of a light beam or a portion of a light beam that is not reflected by, for example, a mirror. A light beam passing through a lens or flat window is considered to be direct light.

  In this disclosure, “approximately” means “very close” or within normal manufacturing tolerances. For example, a substantially flat window is intended to be flat by design, but may differ from perfect flat based on production variations.

  Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

  A laser sustaining plasma lamp includes a pressurized chamber containing an ionizable medium (a noble gas mixture) that is ignited to form a plasma and is maintained by laser light entering the chamber (or envelope) through an entrance window. . As described in the background art, the high intensity light produced by the plasma is emitted from the chamber, for example via an exit window or a waveguide. The plasma lamp chamber is constructed by conventional brazing methods, and for the consistency of envelope and sealing over the lamp life, the operating temperature of the lamp is such that the brazing interface is maintained near or below 300 degrees Celsius. An upper limit must be set. However, such operating temperatures are not ideal for minimizing gas turbulence in the chamber. Also, the brazing material may not be compatible with certain ionizable media. Envelopes in which sapphire windows are welded to sapphire tubes have been difficult and expensive to manufacture (see US 9,230,771 B2).

  The first exemplary embodiment relates to a pressurized laser sustained plasma lamp 300 having a sapphire chamber (or “envelope”). FIG. 3A shows a cross-sectional view of a first exemplary embodiment of a laser sustained plasma lamp 300 and FIG. 3B shows a perspective view of the laser sustained plasma lamp 300. The lamp 300 includes a sapphire tube 310 shown in detail in FIGS. 4A, 4B, and 4C. In the first embodiment, the sapphire tube 310 has a substantially cylindrical shape and includes an inner wall 311 and an outer wall 312. There are two substantially planar sapphire windows 340, 342 that are precision machined, ground, and polished that cover each end of the sapphire tube 310, an entrance sapphire window 340 and an exit sapphire window 342. Each end portion of the sapphire tube 310 has an insertion portion 315 in which the height of the cylindrical outer wall 312 is larger than the height of the cylindrical inner wall 311, and the outer wall 312 projects over the inner wall at both ends of the sapphire tube 310. Including. The flat portion 316 at the first end of the outer wall 312 having an annular surface faces the inner surface 341 of the entrance sapphire window 340 but may not be in direct contact. Similarly, the flat portion 316 at the second end of the outer wall 312 having an annular surface faces the inner surface 343 of the exit sapphire window 342 but may not be in direct contact. The insert 315 provides an annular void volume for receiving the inlet metal sealing ring 320 at the first end of the sapphire tube 310 and the outlet metal sealing ring 322 at the second end of the sapphire tube 310.

  The entrance metal sealing ring 320 may contact and seal between the flat portion 316 of the sapphire tube 310 and the inner surface 341 of the entrance sapphire window 340. Similarly, the exit metal sealing ring 322 may contact and seal between the flat portion 316 of the sapphire tube 310 and the inner surface 343 of the exit sapphire window 342. Preferably, the sapphire tube 310 does not directly contact either the entrance sapphire window 340 or the exit sapphire window 342, but the metal sealing rings 320, 322 are the windows 340, 342 and / or sapphire in both the exit and entrance directions. A very small gap is provided that serves as a buffer for thermal expansion of the tube 310.

  The plug-in portion 315 is illustrated as having an L-shaped cross section, but other configurations such as a curved cross section are possible. The plug-in cross-sectional shape is preferably formed to apply pressure to the metal mechanical seal rings 320, 322 and hold the metal mechanical seal rings 320, 322 between the sapphire windows 340, 342 and the sapphire tube 310.

  Rather than brazing the sapphire windows 340, 342 to the sapphire tube 310, metal mechanical seal rings 320, 322 are provided at each end of the tube 310 to seal between the tube 310 and the windows 340, 342. ing. The metal sealing rings 320, 322 are pressed tightly against the sapphire windows 340, 342 and the sapphire tube 310 to contain an ionizable medium such as xenon and / or krypton and a plasma (on ignition) in the chamber 330. Configured to provide a hermetic seal. The metal sealing rings 320, 322 may be C-shaped, O-shaped, V-shaped or W-shaped, among other possible configurations, preferably 300 series stainless steel, X750 alloy or 718. It is formed of an alloy or the like.

  The metal sealing rings 320, 322 may have a compressibility of about 40 microns. The metal sealing rings 320 and 322 are preferably soft-plated, and even a slight leak may depressurize the cavity 330 over a long period of time. To ensure improved sealing, the joints between the metal sealing rings 320, 322 and the sapphire tube 310 are optionally soft-coated, for example with gold, silver, or (preferably) soft nickel. Also good. The sealing configuration itself is configured to accommodate up to 50,000 psi or higher at temperatures up to 1300F.

  The interface between the sapphire tube 310 and the windows 340, 342 and / or a portion of the metal surface of the metal seal rings 320, 322 may be, for example, gold, silver, or nickel to suppress leakage of ionizable material from the mechanical seal. It may be plated with a soft metal such as. The sapphire tube 310 may have one or more sealable inlets (not shown) for filling and / or discharging ionizable material.

  The chamber assembly 330 can be held in mechanical integration by an external structure that serves as a clamp that applies pressure to the inlet end of the inlet sapphire window 340 and the outlet end of the outlet window 342. This clamping pressure at least partially seals the inlet sapphire window 340 and the sapphire tube 310 by the inlet metal sealing ring 320 and the outlet sapphire window 342 and the sapphire tube 310 by the outlet metal sealing ring 322. Can be used to maintain.

  In the first embodiment, mechanical fastening is performed by welded two-piece sleeve structures 350, 355. As shown in FIG. 5, a tungsten inert gas (TIG) welded metal sleeve and flanged container assembly formed of a first sleeve portion 350 and a second sleeve portion 355 holds the pressure plating chamber 330 assembly together. To do. Suitable metals for the sleeves 350, 355 may be selected to match the sapphire coefficient of thermal expansion over the operating temperature range of the lamp application, such as, for example, amber, inconel, or (preferably) kovar. Other materials can be applied, for example, to manipulate the change in expansion coefficient over temperature and elongation. In some embodiments, combinations of various metals, such as kovar, amber, inconel, and various other irons, can be used to fit the sapphire thermal expansion coefficient when the expansion coefficient is not linear over temperature. 350, 355 can be used.

  The first sleeve portion 350 and the second sleeve portion 355 may have a substantially cylindrical shape, and at least inner portions of the first sleeve portion 350 and the second sleeve portion 355 coincide with the outer wall 312 of the chamber assembly 330.

  The first sleeve portion 350 may include a first inwardly projecting annular lip portion 351 configured to abut the entrance sapphire window 340. Similarly, the second sleeve portion 355 may include a second inwardly projecting annular lip portion 356 configured to abut the exit window 342. When the first sleeve portion 350 is welded to the second sleeve portion 355, the annular lip portion 351 projecting in the first inward applies pressure to the inlet sapphire window 340, and the annular lip portion 356 projecting in the second inward is similarly formed. Pressure is applied to the exit window 342, thereby holding the chamber assembly 330 together.

  The first sleeve portion 350 is configured to mate with the second sleeve portion 355 at a weld joint 370 (FIG. 3A) surrounding the chamber assembly 330. In the first embodiment, the first sleeve portion 350 includes a protruding flange 361 configured to overhang and form an annular recess 360. The annular recess 360 is configured to receive the fitting portion 362.

  In the first embodiment, the first sleeve portion 350 and the second sleeve portion 355 are joined at the welded joint 370 over the projecting flange 361 and the fitting portion 362 on the inside of the annular recess 360, but in other joining configurations. There may be.

  3-5 show a first sleeve portion 350 adjacent to the entrance sapphire window 340 and a second sleeve portion 355 adjacent to the exit window 342, but in an alternative embodiment, the first sleeve portion 350 is adjacent to the exit window 342. The second sleeve portion 355 may be configured to be adjacent to the entrance sapphire window 340.

  In alternative embodiments, for example, for a lamp operating at a maximum pressure of 3500 psi in chamber 330 and operating at a temperature of 300C to about 900C, Kovar or amber can be used as the tube material instead of sapphire. The windows 340 and 342 may have a diameter of 8 mm to 100 mm, for example. In different embodiments, the windows 340, 342 may be coated to transmit and / or reflect desired wavelengths. The windows 340, 342 may be in the form of entrance and / or exit lenses for shaping entrance laser light and / or exit high brightness light.

  In general, the lamp 300 may not include a conventional ignition electrode, such as an electrode that penetrates the sapphire tube 310. Alternatively, the lamp 300 may be ignited by the energy of the entrance laser. In an alternative embodiment, active charge carriers such as Kr-85 and / or internal passively tritated tungsten electrode rings may be housed in chamber 330 to facilitate ignition (ionization of ionizable media).

  As shown in FIG. 6, the assembly and sealing process may be automated and may be performed in a sealed pressurized tooling chamber 600 having a noble gas (Xe, Ar, He, Kr) atmosphere. The movable rod 630 is used to push the windows 340, 342 and the metal sealing rings 320, 322 into the pressurized chamber 330 formed by the windows 340, 342 and the tube 310. The final TIG weld sealing step can be performed under air.

  While the first embodiment includes a chamber assembly 330 having a tube 310, two sapphire windows 340, 342, and two metal sealing rings 320, 322, in a second embodiment (not shown), the chamber assembly includes 1 One open end and one closed end may be provided, and the open end may have a tube sealed with a window and a metal sealing ring as in the first embodiment. Other alternative embodiments are possible where the chamber tube is not welded and is held together by a welded external structure / clamp.

  FIG. 7 shows a flowchart 700 of an exemplary embodiment of a method for forming a sealable pressurized laser sustained plasma lamp 300. It should be noted that any process description or block in the flowchart is understood to represent a module, segment, piece of code, or step that includes one or more instructions for implementing a particular logic function in the process. And, as will be appreciated by those skilled in the art of the present invention, the functions are performed in a different order than that shown or described, including substantially simultaneous or reverse order, depending on the functionality included. Alternative implementations that may be made are within the scope of the present invention.

  As shown in block 710, the components for the lamp 300 (e.g., the chamber assembly 330 including the sleeves 350, 355 and the tube 310, the metal sealing rings 320, 322, and the windows 340, 342) may be at atmospheric pressure, for example. It is arranged inside the jig 610 in the pressurized tooling chamber 600. Here, the components of the chamber assembly 330 are mechanically held in place by the sleeves 350, 355, but the chamber assembly 330 is not functionally sealed.

  As shown in block 720, the pressurized tooling chamber 600 is sealed. As shown in block 730, the pressurized tooling chamber 600 is filled with an ionizable medium that is used to fill the chamber 330 of the lamp 300. The pressurized tooling chamber 600 is then pressurized to, for example, 250-2000 psi. As shown in block 740, the movable rod 630 in the pressurized tooling chamber 600 is provided to form a seal for the chamber assembly 330 by pushing the windows 340, 342 and the metal sealing rings 320, 322 with the sapphire tube 310. It has been. For example, the bar may compress the lamp 300 against the jig 610.

  Once sealing of the chamber assembly 330 is achieved, the tooling chamber is emptied, as shown at block 750. For example, the movable rod 630 presses both the sapphire windows 340, 342 against the metal seal rings 320, 322, and if the seal is engaged, it bends slightly and the seal engagement can be measured. The fill gas (ionizable medium) can be recovered for future filling processes.

  As shown in block 760, the metal sleeve portions 350, 355 are integrally welded, for example, by TIG welding. The movable rod 630 is removed after TIG welding, and the TIG welding sleeves 350 and 355 take over the function of restraining the windows 340 and 342. The TIG welding may not surround the sleeves 350 and 355 360 degrees without a break. For example, a 90% portion or other suitable configuration may be sufficient to maintain the consistency of the sleeves 350, 355 with respect to the design of the pressurized tooling chamber 600. TIG welded metal sleeves 350, 355 serve as clamps to hold windows 340, 342 and sapphire tube 310 against all pressures and are external to sleeves 350, 355 by the internal fill gas pressure of chamber assembly 330. The pushed windows 340, 342 are fully accommodated over the life of the product.

  In an alternative embodiment, rather than TIG welding the metal sleeves 350, 355 together under atmospheric pressure, the metal sleeves 350, 355 are, for example, radio frequency (RF) embedded in at least one of the metal sleeves 350, 355. The coil can be brazed before the tooling chamber is emptied. The current flowing through the RF coil heats the metal sleeve, allowing brazing using a non-ferrous alloy having a melting point lower than that of the metal sleeves 350, 355.

  Although the method described above has been described with respect to sapphire windows and tubes, the method is not limited to sapphire windows and / or sapphire tube ceilings. For example, the method can be applied to sealing sapphire windows (or other material windows) to any high temperature chemically inert tube. This method can be utilized to create a sealed and pressurized environment so that the resulting structure is resistant to plasma temperature and plasma radiation.

  Also, the above-described embodiments facilitate ease of introduction into metal halide, mercury, and other solid lamp chambers to increase operating pressure with metal vapor that directly affects black body color temperature, associated spectrum and radiance. Advantageously.

It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the above, the present invention is intended to cover modifications and variations of the present invention provided they come within the scope of the following claims and their equivalents.

Claims (16)

A chamber tube (310) having an inlet end and an outlet end;
An inlet sapphire window (340) provided at the inlet end of the chamber tube;
A first metal sealing ring (320) configured to seal against the inlet end of the chamber tube and the inlet sapphire window;
An exit sapphire window (342) provided at the exit end of the chamber tube; and a second metal sealing ring (322) configured to seal against the exit end of the chamber tube and the exit sapphire window.
And surrounded by the chamber tube (310), the inlet sapphire window (340), the first metal sealing ring (320), the outlet sapphire window (342) and the second metal sealing ring (322), A mechanical pressure sealed chamber assembly (330) configured to contain an ionizable material;
A mechanical fastening structure (350, 355) external to the chamber assembly configured to span and fasten at least a portion of the entrance sapphire window and the exit sapphire window;
With
The laser sustained plasma lamp (300), wherein the inlet sapphire window and the outlet sapphire window are not connected to the chamber tube by welding and / or brazing.   The lamp of claim 1, wherein the mechanical fastening structure comprises a sleeve having an inner surface that conforms to an outer surface of the chamber tube. The sleeve is
A first sleeve portion (350) provided at the inlet end of the chamber tube;
A second sleeve portion (355) provided at the outlet end of the chamber tube;
The lamp of claim 2, further comprising:   The lamp according to claim 3, wherein the first sleeve portion is TIG welded to the second sleeve portion.   The lamp according to claim 3, wherein the first sleeve portion is brazed to the second sleeve portion.   The lamp of claim 1, wherein the inlet window and / or the outlet window are precision finished, ground, and polished.   The lamp of claim 1, wherein the mechanically sealed pressurized chamber is substantially cylindrical.   The lamp of claim 1, wherein the chamber tube is made of sapphire.   The lamp of claim 1, wherein the first metal sealing ring and / or the second metal sealing ring has a C-shape.   At least a portion of the chamber tube and / or a portion of the inlet and outlet windows configured to contact the first metal sealing ring and / or the second metal sealing ring is plated with a soft metal. The lamp of claim 1.   The lamp of claim 1, wherein the first metal sealing ring and / or the second metal sealing ring is coated with a soft metal. A method of manufacturing a laser sustained plasma lamp, comprising:
Placing a chamber assembly having a chamber tube, a first chamber window, a first chamber seal, a second chamber window, and a second chamber seal in a sleeve assembly comprising a first sleeve portion and a second sleeve portion;
Securing the sleeve assembly and the chamber assembly in a jig in a tooling chamber;
Sealing the tooling chamber;
Filling the tooling chamber with a pressurized ionizable medium;
Compressing the first window, the first seal, the chamber tube, the second seal, and the second window against the jig to seal the chamber assembly;
Emptying the tooling chamber;
Including a method.   The method of claim 12, further comprising welding the first sleeve portion and the second sleeve portion together.   The method of claim 13, wherein the welding is TIG welding.   The method of claim 12, further comprising brazing the first sleeve portion and the second sleeve portion together. A chamber tube having an open inlet end and a closed outlet end;
A sapphire window provided at the open end of the chamber tube;
A metal sealing ring configured to seal against an open end of the chamber tube and the sapphire window;
And a mechanical pressure sealed chamber assembly surrounded by the chamber tube, the sapphire window and the metal sealing ring and configured to receive an ionizable material;
A mechanical fastening structure external to the chamber assembly configured to span and fasten at least a portion of the sapphire window and the tube closed end of the chamber;
With
The sapphire window is a laser-sustained plasma lamp that is not connected to the chamber tube by welding and / or brazing.